U.S. patent number 10,823,859 [Application Number 16/177,631] was granted by the patent office on 2020-11-03 for image sensor.
This patent grant is currently assigned to SHENZHEN XPECTVISION TECHNOLOGY CO., LTD.. The grantee listed for this patent is SHENZHEN XPECTVISION TECHNOLOGY CO., LTD.. Invention is credited to Peiyan Cao, Yurun Liu.
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United States Patent |
10,823,859 |
Cao , et al. |
November 3, 2020 |
Image sensor
Abstract
Disclosed herein is a method, comprising: exposing an image
sensor to a scene; measuring, as analog signals, intensities of
light from the scene by a plurality of pixels of the image sensor;
converting the analog signals to digital signals; and determining a
total intensity of light of the scene by calculating a sum of the
digital signals.
Inventors: |
Cao; Peiyan (Shenzhen,
CN), Liu; Yurun (Shenzhen, CN) |
Applicant: |
Name |
City |
State |
Country |
Type |
SHENZHEN XPECTVISION TECHNOLOGY CO., LTD. |
Shenzhen |
N/A |
CN |
|
|
Assignee: |
SHENZHEN XPECTVISION TECHNOLOGY
CO., LTD. (Shenzhen, CN)
|
Family
ID: |
1000005157068 |
Appl.
No.: |
16/177,631 |
Filed: |
November 1, 2018 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20190072681 A1 |
Mar 7, 2019 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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PCT/CN2016/105809 |
Nov 15, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01T
1/247 (20130101); G01T 1/24 (20130101); H04N
5/378 (20130101); H04N 5/347 (20130101); H04N
5/32 (20130101) |
Current International
Class: |
G01T
1/24 (20060101); H04N 5/347 (20110101); H04N
5/378 (20110101); H04N 5/32 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1098790 |
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Feb 1995 |
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CN |
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104199081 |
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Dec 2014 |
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CN |
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1566959 |
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Aug 2005 |
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EP |
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Primary Examiner: Kao; Chih-Cheng
Attorney, Agent or Firm: IPro, PLLC
Claims
What is claimed is:
1. A method, comprising: exposing an image sensor to a scene;
measuring, as analog signals, intensities of light from the scene
by a plurality of pixels of the image sensor; converting the analog
signals to digital signals; determining residue analog signals from
conversion of the analog signals to the digital signals;
determining a total residue analog signal by summing the residue
analog signals; determining a total residue digital signal by
digitizing the total residue analog signal; determining a total
intensity of light of the scene by summing the digital signals and
the total residue digital signal; wherein the light is visible
light or X-ray.
2. The method of claim 1, wherein an ADC is used in converting the
analog signals to the digital signals.
3. The method of claim 2, wherein the plurality of pixels share the
ADC.
4. The method of claim 3, wherein the plurality of pixels share the
ADC through a multiplexer.
5. The method of claim 2, wherein the ADC uses delta-sigma
modulation.
6. An image sensor, comprising: a plurality of diodes; a first ADC
configured to convert analog signals from the diodes into digital
signals and to output residue analog signals from conversion of the
analog signals to the digital signals; a first circuit configured
to combine the digital signals as a total digital signal; a second
circuit configured to combine the residue analog signals as a total
residue analog signal; a second ADC configured to convert the total
residue analog signal into a total residue digital signal; and a
third circuit configured to combine the total digital signal and
the total residue digital signal.
7. The image sensor of claim 6, further comprising a multiplexer
electrically connected to the diodes.
8. The image sensor of claim 7, wherein the multiplexer is
configured to selectively direct the analog signals from the diodes
to the first ADC.
9. An X-ray computed tomography (X-ray CT) system comprising the
image sensor of claim 6 and an X-ray source.
Description
TECHNICAL FIELD
The disclosure herein relates to image sensors.
BACKGROUND
An image sensor (also referred to as imaging sensor) is a sensor
that detects and conveys the information that constitutes an image.
An image sensor may do so by producing a signal that represents
location-dependent attenuation of light (as the light passes
through or reflect off a medium). The signal is usually an electric
signal such as an electric voltage or current. The light an image
sensor may detect is not limited visible light, but can be
electromagnetic radiation in other wavelengths (e.g., infrared,
ultraviolet, X-ray, gamma ray).
An image sensor may involve converting analog signals to digital
signals. An analog signal is a signal whose time varying feature is
not limited to a set of discrete values; a digital signal is a
signal whose time vary feature is limited to a set of discrete
values. The image sensor thus may include an analog-to-digital
converter (ADC or A/D), which is a device that converts an analog
signal to a digital signal. The ADC may use different coding
schemes in the conversion. Typically the digital signal is a two's
complement binary number that is proportional to the analog signal,
but there are other possible coding schemes.
An ADC is often functionally defined by a few characteristics. One
of these characteristics is the bandwidth, which is the range of
frequencies of the analog signal the ADC can handle. Another is the
dynamic range, which is the difference between the smallest and
largest analog signals the ADC can resolve. The dynamic range is
often measured as a ratio, or as a base-10 (decibel) or base-2
(doublings, bits or stops) logarithmic value. The dynamic range of
an ADC may be affected by many factors, including the resolution
(the number of output levels the ADC can quantize an analog signal
to), linearity and accuracy (how well the quantization levels match
the true analog signal) and jitter (the deviation from true
periodicity of a presumed periodic signal). Another characteristic
is the resolution, which is the number of discrete values the ADC
can produce in the digital signal. Yet another characteristic is
the step size, which is the voltage difference between one digital
level (i.e. 0001) and the next one (i.e. 0010 or 0000).
An image sensor may use scintillators to convert a light it cannot
other detect into a light it can detect. For example, in an image
sensor for X-ray, a scintillator (e.g., sodium iodide) absorbs
incident X-ray and emits visible light and the visible light is
detected. The scintillator may be pixelated for various purposes,
e.g., to limit visible diffusion within the scintillator.
SUMMARY
Disclosed herein is a method, comprising: exposing an image sensor
to a scene; measuring, as analog signals, intensities of light from
the scene by a plurality of pixels of the image sensor; converting
the analog signals to digital signals; and determining a total
intensity of light of the scene by calculating a sum of the digital
signals.
According to an embodiment, the light is visible light.
According to an embodiment, the light is X-ray.
According to an embodiment, an ADC is used in converting the analog
signals to the digital signals.
According to an embodiment, the plurality of pixels share the
ADC.
According to an embodiment, the plurality of pixels share the ADC
through a multiplexer.
Disclosed herein is an image sensor, comprising: a radiation
absorption layer comprising a plurality of diodes; an electronics
layer comprising a circuit configured to combine digital signals
representing electric currents or electric voltages from the
plurality of diodes; and a memory configured to store the combined
digital signals.
According to an embodiment, the image sensor further comprises a
multiplexer electrically connected to the diodes.
According to an embodiment, the multiplexer is configured to
selectively direct analog signals from the diodes to an ADC and the
ADC is configured to convert the analog signals to the digital
signals.
According to an embodiment, the electronics layer comprises an
electronics system for each of the diodes, the electronics system
is configured to convert an analog signal from each of the diodes
into one of the digital signals, and the multiplexer is configured
to selectively direct the analog signals to the circuit.
Disclosed herein is an X-ray computed tomography (X-ray CT) system
comprising any of the above imaging sensors and an X-ray
source.
According to an embodiment, the method further comprises
determining residue analog signals from the conversion of the
analog signals to the digital signals; determining a total residue
analog signal by summing the residue analog signals; determining a
total residue digital signal by digitizing the total residue analog
signal; wherein determining the total intensity comprises
calculating a sum of the digital signals and the total residue
digital signal.
According to an embodiment, the image sensor further comprises
another ADC configured to a total residue analog signal.
According to an embodiment, the ADC uses delta-sigma
modulation.
BRIEF DESCRIPTION OF FIGURES
FIG. 1 schematically shows one pixel of a scintillator may be
imaged by one pixel of an image sensor.
FIG. 2 schematically shows an image sensor, according to an
embodiment.
FIG. 3 shows an exemplary top view of a portion of the image sensor
in FIG. 2, according to an embodiment.
FIG. 4A-FIG. 4D schematically show a scheme of detecting an image
with an image sensor, where the signals from some pixels of the
image sensor are combined.
FIG. 5 schematically shows a flow chart for a method, according to
an embodiment.
FIG. 6 schematically shows a flow chart for a method, according to
an embodiment.
FIG. 7 schematically shows the electronics layer, according to an
embodiment.
FIG. 8 schematically shows a top view of the electronics layer of
FIG. 7, according to an embodiment.
FIG. 9 schematically shows a top view of the electronics layer of
FIG. 7, according to an embodiment.
FIG. 10 schematically shows a top view of the electronics layer of
FIG. 7, according to an embodiment.
FIG. 11 schematically shows an X-ray computed tomography (X-ray CT)
system comprising the image sensor described herein, according to
an embodiment.
DETAILED DESCRIPTION
As FIG. 1 schematically shows, a pixel 910 of a scintillator is
exposed to incident X-ray. The pixel 910 absorbs the X-ray and
emits visible light. The visible light from the entire pixel 910 of
the scintillator is directed to a pixel 920 of an image sensor
configured to detect visible light. The visible light emitted from
the pixel 910 of the scintillator is not spatially resolved by the
pixel 920 of the image sensor; the visible light emitted from the
pixel 910 of the scintillator is instead integrated and the pixel
920 of the image sensor detects the total amount of the visible
light. The image sensor has an ADC that converts the amount of the
visible light detected by the pixel 920 into a digital signal. The
larger the pixel 910 of the scintillator is, the larger the total
amount of the visible light emitted therefrom tends to be, and thus
the larger the dynamic range of the ADC should be.
FIG. 2 schematically shows an image sensor 100, according to an
embodiment. The image sensor 100 may include a radiation absorption
layer 110 and an electronics layer 120 (e.g., an ASIC) for
processing or analyzing electrical signals incident radiation
generates in the radiation absorption layer 110. The radiation
absorption layer 110 may include a semiconductor material (e.g.,
silicon, germanium). The radiation absorption layer 110 may include
one or more diodes (e.g., p-i-n or p-n) formed by a first doped
region 111, one or more discrete regions 114 of a second doped
region 113. The second doped region 113 may be separated from the
first doped region 111 by an optional the intrinsic region 112. The
discrete portions 114 are separated from one another by the first
doped region 111 or the intrinsic region 112. The first doped
region 111 and the second doped region 113 have opposite types of
doping (e.g., region 111 is p-type and region 113 is n-type, or
region 111 is n-type and region 113 is p-type). In the example in
FIG. 2, each of the discrete regions 114 of the second doped region
113 forms a diode with the first doped region 111 and the optional
intrinsic region 112. Namely, in the example in FIG. 2, the
radiation absorption layer 110 has a plurality of diodes having the
first doped region 111 as a shared electrode. The first doped
region 111 may also have discrete portions. In an example, the
image sensor 100 may be used to detect visible light emitted from
the pixel 910 of a scintillator, where multiple discrete portions
114 are within the footprint of the pixel 910 of the scintillator,
by combining the signals obtained from these multiple discrete
portions 114.
When a photon hits the radiation absorption layer 110 including
diodes, it may be absorbed and generate one or more charge carriers
by a number of mechanisms. For example, an X-ray photon may
generate 10 to 100000 charge carriers. The charge carriers may
drift to the electrodes of one of the diodes under an electric
field. The field may be an external electric field, for example,
between electrical contacts 119A and 119B. For detection of visible
light, the electrical contacts 119A may be a grid of metal or
heavily doped semiconductor; the electrical contacts 119A may be a
transparent material such as indium tin oxide. The electrical
contact 119B may include discrete portions each of which is in
electrical contact with the discrete regions 114. In an embodiment,
the charge carriers may drift in directions such that the charge
carriers generated by a single photon are not substantially shared
by two different discrete regions 114 ("not substantially shared"
here means less than 2%, less than 0.5%, less than 0.1%, or less
than 0.01% of these charge carriers flow to a different one of the
discrete regions 114 than the rest of the charge carriers). A pixel
150 associated with a discrete region 114 (or associated with the
diode that comprise this discrete region 114) may be an area around
the discrete region 114 in which substantially all (more than 98%,
more than 99.5%, more than 99.9%, or more than 99.99% of) charge
carriers generated by a photon incident therein flow to that
discrete region 114. Namely, less than 2%, less than 1%, less than
0.1%, or less than 0.01% of these charge carriers flow beyond the
pixel.
By measuring the drift current flowing into each of the discrete
regions 114, or the rate of change of the voltage of each of the
discrete regions 114, the number of photons absorbed (which relates
to the incident radiation intensity) and/or the energies thereof in
the pixels associated with the discrete regions 114 may be
determined. The pixels may be organized in any suitable array, such
as, a square array, a triangular array and a honeycomb array. The
pixels may have any suitable shape, such as, circular, triangular,
square, rectangular, and hexangular. The pixels may be individually
addressable.
The electronics layer 120 may include an electronics system 121
suitable for processing or interpreting signals generated by
photons incident on the radiation absorption layer 110. The
electronics system 121 may include an analog circuitry such as a
filter network, amplifiers, integrators, and comparators, or a
digital circuitry such as a microprocessors, and memory. The
electronics system 121 may include components shared by the pixels
or components dedicated to a single pixel. For example, the
electronics system 121 may include an amplifier dedicated to each
pixel and a microprocessor shared among all the pixels. The
electronics system 121 may be electrically connected to the pixels
by vias 131. Space among the vias may be filled with a filler
material 130, which may increase the mechanical stability of the
connection of the electronics layer 120 to the radiation absorption
layer 110. Other bonding techniques are possible to connect the
electronics system 121 to the pixels without using vias. The
electronics system 121 may be configured to count photons by the
pixels or configured to measure the amounts of charge carriers
accumulated at the pixels (e.g., by using an analog-to-digital
converter (ADC) shared by the pixels).
FIG. 3 schematically shows that the image sensor 100 may have an
array of pixels 150. The array may be a rectangular array, a
honeycomb array, a hexagonal array or any other suitable array.
Each pixel 150 may be configured to detect (e.g., with the
associated diode) a photon incident thereon, measure the energy of
the photon, or both. For example, each pixel 150 may be configured
to count numbers of photons incident thereon whose energy falls in
a plurality of bins, within a period of time. All the pixels 150
may be configured to count the numbers of photons incident thereon
within a plurality of bins of energy within the same period of
time. Each pixel 150 may have its own electronics system 121
configured to convert an analog signal representing the energy of
an incident photon or the intensity of the incident light onto that
pixel 150 to a digital signal. The electronics system 121 may
include an ADC. The pixels 150 may have a shared ADC. The ADC may
have a resolution of 10 bits or higher. The electronics system 121
for each pixel 150 may be configured to measure its dark current,
such as before or concurrently with each photon incident thereon.
The electronics system 121 for each pixel 150 may be configured to
deduct the contribution of the dark current from the energy of the
photon incident thereon. The electronics system 121 for each pixel
150 may be configured to operate in parallel. For example, when one
pixel 150 measures an incident photon, another pixel 150 may be
waiting for a photon to arrive. The pixels 150 may be but do not
have to be individually addressable.
According to an embodiment, the image sensor 100 may be configured
to combine the digital signals from multiple pixels 150. FIG. 4A
schematically shows that the total intensity of incident light in
an area 1100 is "1000." The incident light in the area 1100 is
detected by an array of pixels 150. FIG. 4B schematically shows
that intensities of light detected by the pixels 150 in the array,
the total of which is the same as the total intensity of incident
light of "1000" in the area 1100. The intensities of light detected
by the pixels 150 in the array may be analog signals. The intensity
of light detected by each of the pixels 150 tends to be much lower
than the total intensity of incident light in the area 1100. In
this example, the maximum of the intensities of light detected by
the pixels 150 is less than 10% of the total intensity of light.
The FIG. 4C schematically shows the digital signals converted from
the intensities of light detected by the pixels 150 in the array.
Because the intensities of light detected by the pixels 150 in the
array are usually much smaller than the total intensity, an ADC
needed to convert these intensities of light detected by the pixels
would have much fewer bits than an ADC needed to convert the total
intensity of light in the area 1100, at the same step size. FIG. 4D
schematically shows that the sum (in binary number 01111101000 in
this example) of the digital signals is the same as a digital
signal that would have been converted from the total intensity of
light "1000."
FIG. 5 schematically shows a flow chart for a method, according to
an embodiment. In procedure 5010, an image sensor is exposed to a
scene. In procedure 5020, intensities of light are measured as
analog signals by the pixels of the image sensor. The light may be
from a scene of visible light or other electromagnetic radiation
(e.g., X-ray). For example, the light may be visible light from a
scintillator exposed to X-ray. In procedure 5030, the analog
signals are converted to digital signals by an ADC, the digital
signals representing the intensities of light the pixels measured.
The pixels may share this ADC, for example, through a multiplexer.
In procedure 5040, a total intensity of light in the scene is
determined by calculating a sum of the digital signals. The ADC
used to convert the analog signal representing the intensities
measured by the pixels does not need as many bits as an ADC
suitable for converting the total intensity of light in the scene,
at the same step size.
FIG. 6 schematically shows a flow chart for a method, according to
an embodiment. Intensities of light are measured as analog signals
by the pixels of the image sensor. Each of the pixels has a first
ADC in the electronics system 121. The analog signals (e.g., 6010A,
6010B, 6010C, etc.) are digitized in procedure 6020A, 6020B, 6020C,
etc., respectively, to digital signals 6030A, 6030B, 6030C, etc.
and residue analog signals 6040A, 6040B, 6040C, etc. The residue
analog signals are below the magnitude of the least significant bit
(LSB) voltage of the first ADC. As schematically shown in FIG. 6,
the analog signals 6010A, 6010B and 6010C respectively are
digitized to digital signals 6030A (in this example, the digital
signal 6030A equals 5), 6030B (in this example, the digital signal
6030B equals 4), 6030C (in this example, the digital signal 6030C
equals 1); the residue analog signals 6040A, 6040B, 6040C have
different magnitudes. The digital signals of the pixels are then
summed as a total digital signal 6050 (in this example, the total
digital signal 6050 equals 10=5+4+1). The residue analog signals
6040A, 6040B, 6040C, etc. are summed as a total residue analog
signal 6060. In procedure 6070, the total residue analog signal
6060 is digitized by a second ADC the pixels share to a total
residue digital signal 6080 (in this example, the total residue
digital signal 6080 equals 1). The total residue digital signal
6080 and the total digital signal 6050 are summed as a total signal
6090 (in this example, the total signal 6090 equals 11=10+1).
The ADCs in the image sensor 100 may use delta-sigma (sigma-delta,
.DELTA..SIGMA. or .SIGMA..DELTA.) modulation. In a conventional
ADC, an analog signal is integrated, or sampled, with a sampling
frequency and subsequently quantized in a multi-level quantizer
into a digital signal. This process introduces quantization error
noise. The first step in a delta-sigma modulation is delta
modulation. In delta modulation the change in the signal (its
delta) is encoded, rather than the absolute value. The result is a
stream of pulses, as opposed to a stream of numbers. The digital
output (i.e., the pulses) is passed through a 1-bit DAC and the
resulting analog signal (sigma) is added to the input signal of the
ADC. In flow of FIG. 6, during the integration of the analog signal
(e.g., 6010A, 6010B, 6010C, etc.) on each pixel and reaches the
delta, a counter is increased by one and the delta is deducted from
the analog signal. At the end of the integration, the registered
value of the counter is the digital signal (e.g., 6030A, 6030B,
6030C, etc.) and the remaining analog signal smaller than the delta
is the residue analog signal (e.g., 6040A, 6040B, 6040C, etc.).
FIG. 7 schematically shows the electronics layer 120 according to
an embodiment. The electronics layer 120 comprises a substrate 122
having a first surface 124 and a second surface 128. A "surface" as
used herein is not necessarily exposed, but can be buried wholly or
partially. The electronics layer 120 comprises one or more electric
contacts 125 on the first surface 124. The one or more electric
contacts 125 may be configured to be electrically connected to one
or more electrodes of the radiation absorption layer 110. The
electronics system 121 may be in or on the substrate 122. The
electronics layer 120 comprises one or more vias 126 extending from
the first surface 124 to the second surface 128. The electronics
layer 120 comprises a redistribution layer (RDL) 123 on the second
surface 128. The RDL 123 may comprise one or more transmission
lines 127. The electronics system 121 is electrically connected to
the electric contacts 125 and the transmission lines 127 through
the vias 126.
The substrate 122 may be a thinned substrate. For example, the
substrate may have at thickness of 750 microns or less, 200 microns
or less, 100 microns or less, 50 microns or less, 20 microns or
less, or 5 microns or less. The substrate 122 may be a silicon
substrate or a substrate or other suitable semiconductor or
insulator. The substrate 122 may be produced by grinding a thicker
substrate to a desired thickness.
The one or more electric contacts 125 may be a layer of metal or
doped semiconductor. For example, the electric contacts 125 may be
gold, copper, platinum, palladium, doped silicon, etc.
The vias 126 pass through the substrate 122 and electrically
connect electrical components (e.g., the electrical contacts 125)
on the first surface 124 to electrical components (e.g., the RDL)
on the second surface 128. The vias 126 are sometimes referred to
as "through-silicon vias" although they may be fabricated in
substrates of materials other than silicon.
The RDL 123 may comprise one or more transmission lines 127. The
transmission lines 127 electrically connect electrical components
(e.g., the vias 126) in the substrate 122 to bonding pads at other
locations on the substrate 122. The transmission lines 127 may be
electrically isolated from the substrate 122 except at certain vias
126 and certain bonding pads. The transmission lines 127 may be a
material (e.g., Al) with small mass attenuation coefficient for the
X-ray energy of interest. The RDL 123 may redistribute electrical
connections to more convenient locations.
FIG. 8 schematically shows a top view of the electronics layer 120
of FIG. 7, according to an embodiment. The electronics layer 120
may have a multiplexer 132. The multiplexer 132 is electrically
connected to the diodes in the radiation absorption layer 110
through the electrical contacts 125 in an area 129 and configured
to selectively direct analog signals from the diodes one by one to
an ADC 133. The electrical contacts 125 may be bonded to the
electrical contacts 119B. The analog signals on the electrical
contacts 125 thus may be the analog signals (e.g., electric current
or voltage) of the diodes in the radiation absorption layer 110.
The ADC 133 converts the analog signals to digital signals. The
digital signals output from the ADC 133 are directed to a circuit
134 (e.g., an arithmetic logic unit (ALU)) configured to combine
the digital signals. The combined digital signals are stored in a
memory 135.
FIG. 9 schematically shows a top view of the electronics layer 120
of FIG. 7, according to an embodiment. The electronics system 121
for each pixel 150 has a built-in ADC 133. The pixels 150 do not
share an ADC. The ADC 133 converts an analog signal (e.g., electric
current or voltage from the diode in that pixel 150) to a digital
signal. The electrical contacts 125 may be bonded to the electrical
contacts 119B. The digital signals on the electrical contacts 125
thus may be the digital signals output from the built-in ADC. The
electronics layer 120 may have a multiplexer 132. The multiplexer
132 is electrically connected to the diodes in the radiation
absorption layer 110 through the electrical contacts 125 in an area
129 and configured to selectively direct digital signals from the
diodes one by one to a circuit 134 (e.g., an arithmetic logic unit
(ALU)) configured to combine the digital signals. The combined
digital signals are stored in a memory 135.
FIG. 10 schematically shows a top view of the electronics layer 120
of FIG. 7, according to an embodiment. The electronics layer 120
has a two-stage ADC such as a sigma-delta ADC. The electronics
system 121 for each pixel 150 has a built-in ADC 133 as the first
stage. The ADC 133 converts an analog signal (e.g., electric
current or voltage from the diode in that pixel 150) to a digital
signal. The electrical contacts 125 may be bonded to the electrical
contacts 119B. The digital signals on the electrical contacts 125
thus may be the digital signals output from the built-in ADC 133.
The electronics layer 120 may have a multiplexer 132. The
multiplexer 132 is electrically connected to the diodes in the
radiation absorption layer 110 through the electrical contacts 125
in an area 129. The multiplexer 132 is configured to selectively
direct digital signals from the diodes one by one to a circuit 134D
(e.g., an arithmetic logic unit (ALU)) configured to combine the
digital signals as a total digital signal. The multiplexer 132 is
configured to selectively direct residue analog signals of the
built-in ADC 133 one by one to a circuit 134A configured to combine
the residue analog signals as a total residue analog signal. The
total residue analog signal is fed into an ADC 137 as the second
stage. The ADC 137 is shared by the pixels 150. The ADC 137
digitizes the total residue analog signal as a total residue
digital signal. The total residue digital signal and the total
digital signal are combined at a circuit 134T as a total signal.
The total signal is stored in a memory 135.
FIG. 11 schematically shows an X-ray computed tomography (X-ray CT)
system. The X-ray CT system uses computer-processed X-rays to
produce tomographic images (virtual "slices") of specific areas of
a scanned object. The tomographic images may be used for diagnostic
and therapeutic purposes in various medical disciplines, or for
flaw detection, failure analysis, metrology, assembly analysis and
reverse engineering. The X-ray CT system comprises the image sensor
100 described herein and an X-ray source 1701. The image sensor 100
and the X-ray source 1701 may be configured to rotate synchronously
along one or more circular or spiral paths.
While various aspects and embodiments have been disclosed herein,
other aspects and embodiments will be apparent to those skilled in
the art. The various aspects and embodiments disclosed herein are
for purposes of illustration and are not intended to be limiting,
with the true scope and spirit being indicated by the following
claims.
* * * * *